Coal companies, utilities, economists and environmentalists are vying to shape legislation that could rechannel hundreds of billions of dollars from one part of the economy to others. The sense of urgency has been heightened by House Energy and Commerce Committee Chairman Henry A. Waxman's push to have a bill ready by the end of May; the California Democrat plans to circulate a draft in about two weeks.

Because of regional differences in energy sources, the political lines are blurred, potentially uniting Democrats and Republicans from states heavily dependent on coal plants against other parts of the nation looking for alternatives.

Most lawmakers and climate activists embrace an approach to limiting greenhouse gas emissions known as cap-and-trade, which would set and gradually lower a limit on nationwide emissions while letting companies buy and sell rationing allowances. But some economists have lined up with big oil companies such as Exxon Mobil, which has endorsed a carbon tax instead. Seven House Democrats, including House Democratic Caucus Chairman John B. Larson (Conn.), introduced a carbon tax measure this week.

Either way, climate legislation will aim to reduce emissions by putting a price on carbon, raising the cost of everything from gasoline to plastics to electricity.

Opposing sides are striving to either frighten or woo voters with talk of whether climate legislation should be viewed as a big ill-timed tax or whether it will unlock new industries and technologies to make the economy more efficient and less dependent on foreign oil. On Tuesday, White House spokesman Robert Gibbs called it "a market-based solution that will drive us to energy independence and create . . . an even more robust market for alternative fuels." Earlier, House Minority Leader John A. Boehner (Ohio) said " 'cap-and-trade' is code for increasing taxes, killing American jobs and raising energy costs for consumers."

Even companies are divided. The owners of nuclear power generators, which don't emit carbon dioxide, are at odds with utilities that rely on coal. And the emerging wind and solar industries are gaining a powerful voice as well.

"There's no end of the political fault lines and there's going to be a heavy burden for the White House," said Philip Sharp, president of Resources for the Future and a former House member.

The Obama administration's budget includes an outline of a relatively simple plan that, starting in 2011, would establish a cap on the quantity of emissions and auction off the right to emit pollutants. It would give the bulk of the money back to lower- and middle-income Americans through a means-tested tax credit. It would set aside a portion of auction revenue for aiding households and industries in regions hurt most by higher costs. It would also reserve a modest portion for research and development. The administration says it wants the program to be revenue-neutral.

At the center of the political battle in Congress are Democratic lawmakers like Sens. Sherrod Brown (Ohio), whose state relies on coal-fired plants for 86 percent of its electricity; Evan Bayh (Ind.), whose state gets 94 percent of its electricity from coal; and Byron L. Dorgan (N.D.), whose state both relies on and exports coal-fired electricity and also has large wind potential. Republican lawmakers in the thick of the battle include Maine's Sens. Susan Collins and Olympia J. Snowe.

"I believe there's something happening in respect to our climate, and we ought to address that," said Dorgan, who chairs the Senate Appropriations subcommittee on energy. "The Congress is intent on doing something, but how quickly and how much, I don't think is clear yet."